For increasingly numerous vehicles, it is becoming possible to gain access to the passenger compartment and to the trunk of the vehicle without having to use a mechanical key or to send a signal to the vehicle by pressing a button. For this purpose it suffices to carry an electronic card, also called a “badge”, which is compatible with the vehicle. An exchange of electromagnetic signals is carried out between the badge and the vehicle in order to allow the vehicle to identify the badge as being a badge authorizing access to the vehicle. In general, the vehicle transmits low-frequency (also called “LF” to represent “Low Frequency”) signals at a frequency usually of the order of 125 kHz. The badge itself responds by generally transmitting signals of the radio frequency, or RF, type at a frequency of the order of 433 MHz. The vehicle of course comprises a receiver for the signals transmitted by the badge and, conversely, the badge also comprises a receiver for the signals transmitted by the vehicle.
New hands-free systems offer not only hands-free unlocking of the vehicle but also hands-free locking of the vehicle. The problems to be solved for managing the automatic locking of the vehicle are more complex than those for managing its unlocking.
It is known, for example, in order to achieve the automatic locking of a vehicle, to establish a bidirectional dialogue between the badge and the vehicle at radio frequency, that is to say using a frequency of the order of 433 MHz. In this case, the range of the signals is relatively large in both directions (of the order of between ten and several tens of meters). The hands-free access management system then detects the badge's exit from the RF transmission zone of the vehicle. When this exit is detected, the locking of the vehicle is commanded. This technology has disadvantages, on the one hand because the range of the RF signals is not well controlled and, on the other hand, because the zone thus defined around the vehicle is relatively large. In many cases, the driver does not perceive the locking of his vehicle, for example signaled by the lighting of the flashing indicators. He therefore leaves his vehicle without being certain of its locking.
In the contrary case in which a smaller zone is defined around the vehicle, for example by using LF technology, the driver perfectly perceives a return from his vehicle at the time of the locking. On the other hand, this locking can be too quick for a passenger getting out of the vehicle after the driver has left the LF transmission zone. In certain cases, for example if a passenger accompanies the driver of the vehicle, an automatic locking is desired. On the other hand, if for example the passenger gets out of the vehicle solely to gain access to its trunk, locking is not desired.
Whatever the extent of the zone defined around the vehicle may be, problems arise when the vehicle is locked by the hands-free system and consequently a door is opened and closed without using the hands-free function and in the absence of a badge in the zone defined around the vehicle.
The idea of the present invention is therefore to provide a specific method, hereafter called the relocking method, which manages such eventualities.